Program Director/Principal Investigator (Last, First, Middle): De La Torre, Juan C. 1R01 AI075298-01A2 Viruses can induce a variety of disease states in the central nervous system. Meningitis is a potentially fatal disorder induced by a long list of human pathogens, including viruses, and is often associated with symptoms that include fever, headache, stiffness of the neck, and seizures. Presently, very little can be done for patients with viral meningitis other than to relieve symptoms. We propose that a detailed understanding of this pathogenic process in real time may foster the development of novel interventions to alleviate symptoms and prevent permanent neurological dysfunction and fatalities. To accomplish this goal we propose to study the well-described meningitis induced by lymphocytic choriomeningitis virus (LCMV), a noncytopathic mouse as well as human pathogen. Intracerebral inoculation of mice with LCMV results in a fatal meningitis within 6 days that is mediated almost entirely by cytotoxic lymphocytes (CTL). Importantly, this disease can be completely prevented by prior vaccination or immunization. The dynamics of cellular interactions in the meninges during failed or effective control of infection have not been studied previously. Moreover, the precise mechanisms that mediate fatal injury in this model are not entirely understood. We will utilize a combination of state-of-the art viral reverse genetics, fluorescently-tagged immune cells, and two-photon laser scanning microscopy in combination with in situ staining for different molecular species to follow the local immune cell dynamics in the LCMV-infected mouse cerebral cortex and meningeal space. Our hypothesis is that CTL damage to astrocyte networks in the CNS leads to generalized fatal seizure during acute LCMV-induced meningitis, and that rapid responsiveness and the use of alternative effector mechanisms by activated memory T cells in vaccinated mice results in limited damage to astrocyte networks, maintenance of the blood brain barrier, and survival. This hypothesis will be addressed by the two focused following specific aims: 1) Completion of the first real time analyses of interactions between CTL and CNS targets infected by fluorescently-tagged LCMV, and 2) in vivo evaluation of immunological synapse formation and molecular mechanisms involved in CNS CTL targeting and damage.